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| -rw-r--r-- | doc/design/timing.tex | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/doc/design/timing.tex b/doc/design/timing.tex index d71b48f23..0b6d73f3a 100644 --- a/doc/design/timing.tex +++ b/doc/design/timing.tex @@ -8,7 +8,8 @@ We are trying to implement full-ish playlist based content specification. The t Frame rates of things can vary a lot; content can be in pretty much anything, and DCP video and audio frame rates may change on a whim depending on what is best for a given set of content. This suggests -(albeit without strong justification) the need for a frame-rate-independent unit of time. +(albeit without strong justification) the need for a +frame-rate-independent unit of time. So far we've been using a time type called \texttt{Time} expressed in $\mathtt{TIME\_HZ}^{-1}$; e.g. \texttt{TIME\_HZ} units is 1 second. @@ -74,4 +75,20 @@ will obviate the need for things to be recalculated when DCP rate changes. On the plus side, lengths in \texttt{Time} are computed on-demand from lengths kept as source frames. + +\section{More musings} + +In version 2 things we changed, and a problem appeared. We have / had +\texttt{ContentTime} which is a metric time type, and it is used to +describe video content length (amongst other things). However if we +load a set of TIFFs and then change the frame rate we don't have the +length in frames i order to work out the new rate. + +This suggests that the content lengths, at least, should be described +in frames. Then to get metric lengths you would need to specify a +timecode. + +I will probably have to try a frame-based ContentTime and see what +problems arise. + \end{document} |